Issue #2068: updated RedundantModifier documentation for final in enums

src/main/java/com/puppycrawl/tools/checkstyle/checks/modifier/RedundantModifierCheck.java

@@ -53,7 +53,26 @@ import com.puppycrawl.tools.checkstyle.utils.CommonUtils;
  *
  * <p>Enums by definition are static implicit subclasses of java.lang.Enum&#60;E&#62;.
  * So, the <code>static</code> modifier on the enums is redundant. In addition,
- * if enum is inside of interface, <code>public</code> modifier is also redundant.
+ * if enum is inside of interface, <code>public</code> modifier is also redundant.</p>
+ *
+ * <p>Enums can also contain abstract methods and methods which can be overridden by the declared
+ * enumeration fields.
+ * See the following example:</p>
+ * <pre>
+ * public enum EnumClass {
+ *    FIELD_1,
+ *    FIELD_2 {
+ *        &#64;Override
+ *        public final void method1() {} // violation expected
+ *    };
+ *
+ *    public void method1() {}
+ *    public final void method2() {} // no violation expected
+ * }
+ * </pre>
+ *
+ * <p>Since these methods can be overridden in these situations, the final methods are not
+ * marked as redundant even though they can't be extended by other classes/enums.</p>
  *
  * <p>Final classes by definition cannot be extended so the <code>final</code>
  * modifier on the method of a final class is redundant.

src/test/java/com/puppycrawl/tools/checkstyle/checks/modifier/RedundantModifierCheckTest.java

@@ -223,4 +223,11 @@ public class RedundantModifierCheckTest
         };
         verify(checkConfig, getPath("InputFinalInAbstractMethods.java"), expected);
     }
+
+    @Test
+    public void testEnumMethods() throws Exception {
+        final DefaultConfiguration checkConfig = createCheckConfig(RedundantModifierCheck.class);
+        final String[] expected = CommonUtils.EMPTY_STRING_ARRAY;
+        verify(checkConfig, getPath("InputFinalInEnumMethods.java"), expected);
+    }
 }

src/test/resources/com/puppycrawl/tools/checkstyle/checks/modifier/InputFinalInEnumMethods.java

@@ -0,0 +1,32 @@
+package com.puppycrawl.tools.checkstyle.checks.modifier;
+
+public enum InputFinalInEnumMethods {
+    E1,
+    E2 {
+        @Override
+        public final void v() {
+        }
+    };
+
+    public void v() {
+    }
+
+    // not redundant since field can override this method if 'final' is removed
+    // and that may not be desirable
+    public final void v2() {
+    }
+}
+enum InputFinalInEnumMethods2 {
+    E1 {
+        @Override
+        public final void v() {
+        }
+    },
+    E2 {
+        @Override
+        public void v() {
+        }
+    };
+
+    public abstract void v();
+}

src/xdocs/config_modifier.xml

@@ -186,6 +186,30 @@
           if enum is inside of interface, <code>public</code> modifier is also redundant.
         </p>
 
+        <p>
+          Enums can also contain abstract methods and methods which can be overridden by the declared
+          enumeration fields.
+          See the following example:
+        </p>
+
+        <source>
+          public enum EnumClass {
+             FIELD_1,
+             FIELD_2 {
+                 &#64;Override
+                 public final void method1() {} // violation expected
+             };
+
+             public void method1() {}
+             public final void method2() {} // no violation expected
+          }
+        </source>
+
+        <p>
+          Since these methods can be overridden in these situations, the final methods are not
+          marked as redundant even though they can't be extended by other classes/enums.
+        </p>
+
         <p>
           Nested <code>enum</code> types are always static by default.
         </p>